CONTROLS ON RESERVOIR DISTRIBUTION, ARCHITECTURE AND STRATIGRAPHIC TRAPPING IN SLOPE SETTINGS

Abstract

Submarine sand reservoir distribution and architecture across slope and base-of-slope systems vary as a function of accommodation, sediment flux rates, substrate mobility and sand-mud content. Slopes evolve through time depending on rates of substrata mobility and sediment flux. Above-grade slopes with ponded accommodation are associated with highly mobile substrata and episodic or relatively low sediment flux. Stepped slopes are associated with less mobile substrata and relatively high rates of sediment flux. Graded slopes are associated with less mobile substrata. Sheet sand deposition on above-grade slopes results from ponded basin 'fill-and-spill' processes. Pinchout of ponded sands into slope drapes deposited around ponded basins form lateral seals for the onlap traps common in this setting. Sheet sands are also found in basin floor positions and at the toes of graded (unconfined) slopes associated with stable substrates. The break in slope onto the basin floor provides a key setting for the deposition of both sheet and channel sands. Pinchout of sands or onlap onto the slope form the updip stratigraphic components forming stratigraphic traps with the potential for large hydrocarbon accumulations.